1. Field of the Invention
The present invention relates to a system of ordering and supplying masks to be used in the process of manufacturing semiconductor devices. In particular, the present invention relates to a system of supplying photomasks to be used as plates for photolithography in the process of manufacturing semiconductor devices.
2. Description of the Background Art
A photomask constituted of a synthetic quartz substrate covered with shielding patterns formed of a thin metal film has been produced for use as a plate for a photolithography step which is one of the steps for manufacturing such a semiconductor integrated circuit device as IC (integrated circuit) chip.
The photomask is produced by a certain mask manufacturer. Information about the specification of the photomask is sent by being recorded on a magnetic tape for example or transmitted online from an IC chip manufacturer (order-sender) to the mask manufacturer (order-receiver). Then, the mask manufacturer prepares production data for producing the photomask according to the supplied information about the specification. With regard to information about details of the order such as the number of ordered photomasks and the delivery date, the IC chip manufacturer (order-sender) notifies the mask manufacturer (order-receiver) by telephone or online. In accordance with the information about order details, the mask manufacturer prepares control data including information necessary for quality control as well as information necessary for production control such as the product number, the number of products to be manufactured, the destination of delivery and the delivery date for example. The prepared control data is passed to a photomask production line. Following the production data prepared according to the specification and the control data prepared according to the information about order details, photomasks are produced on the photomask production line. The photomasks are produced by means of an electron beam exposure machine controlled by the production data for example.
FIG. 30 shows a reticle 8000 for an optical stepper as one example of photomasks as described above. Reticle 8000 constituted of a synthetic quartz substrate has one side on which circuit patterns 8010 and 8020 formed of a thin metal film are provided as a set of shielding patterns.
Actually, circuit patterns 8010 and 8020 each have a set of many patterns with the line-width of the order ranging from a few microns or submicrons to 0.1 micron, for example, which is not shown in FIG. 30.
In manufacturing photomasks, the mask manufacturer should measure and evaluate the production error, i.e., the error (difference) between the design dimension and the finished dimension of an actually produced shielding pattern.
FIGS. 31A and 31B show an element pattern 8100 included in circuit pattern 8010 on the photomask as well as how the dimension of this element pattern 8100 is measured.
In FIG. 31A, this element pattern is rectangular in shape. A measurement window 8200 shown in FIG. 31B is used for measuring the dimension of element pattern 8100.
If the dimension of element pattern 8100 is measured by an SEM (scanning electron microscope), xe2x80x9cmeasurement windowxe2x80x9d refers to a measuring region which is scanned with an electron beam and a resultant electron beam reflection image is observed to measure the dimension of element pattern 8100.
If element pattern 8100 is measured by a laser microscope, xe2x80x9cmeasurement windowxe2x80x9d refers to a measuring region to which a laser beam is directed and a resultant optical image is observed to measure the dimension of element pattern 8100.
Thus, a larger xe2x80x9cmeasurement windowxe2x80x9d provides a greater amount of measurement data which improves the accuracy of the measured dimension.
Regardless of the measurement by means of the electron beam reflection image and the optical image, the observed image in measurement window 8200 is provided as electronic data to a computer and the data of the observed image is image-processed to detect edge parts 8220 and 8210 of element pattern 8100 and measure the dimension thereof. For example, the second derivative of the intensity of the electron beam reflection image may be determined to detect the point of inflection of the reflection intensity and detect the edges from point of inflection.
In this way, the dimension is measured to evaluate any production error of photomasks.
However, if the mask manufacturer is required to evaluate the production error measured as described above and then deliver products to the IC chip manufacturer with the error guaranteed by the mask manufacturer and accordingly required to measure all dimensions of circuit patterns 8010 and 8020, a resultant problem is that the delivery date (turnaround time: TAT) is extended and the production cost increases.
The mask pattern is produced based on design data prepared as digital data. Accordingly, the outline of each pattern is represented, for example, by a set of coordinates on a so-called xe2x80x9cdesign gridxe2x80x9d consisting of units formed by parallel bars and crossbars, one unit corresponding to the minimum design unit. Such a xe2x80x9cdesign gridxe2x80x9d is also called xe2x80x9caddress unitxe2x80x9d for specifying positions where patterns are to be formed in producing a mask.
Each pattern on the photomask being produced is not necessarily formed of outer lines that are parallel with the bars or crossbars of the grid of xe2x80x9caddress unitxe2x80x9d described above. For example, the pattern could have an outer line diagonal to the bars or crossbars or curved outline depending on cases.
For example, an interconnection diagonal to any bar of the design grid at an angle of 45xc2x0 may be formed or a pattern of an element for which a high withstand voltage is required may be designed to have a circular outline.
In this case, the design data used for producing the mask is actually represented as a set of coordinates on a grid having values rounded by xe2x80x9caddress unit.xe2x80x9d
In such a case, the production error between the designed pattern and any shielding pattern on the photomask is affected by round-off error. Therefore, it could be difficult to accurately evaluate manufacturing tolerance as an error between the dimension of the designed pattern and the finished dimension of the shielding pattern.
Moreover, even if outer lines of each pattern on the photomask are all in parallel with the bars or crossbars of the grid of xe2x80x9caddress unit,xe2x80x9d the pattern on the photomask could be complex in shape.
For example, with the decreasing feature size of circuit patterns, it becomes difficult to faithfully form the pattern shape of the mask on a wafer. Then, graphics could be added to the mask pattern or optical proximity correction (OPC) could be applied for correcting the size depending on density of features. In this case, each pattern on the photomask could be complex in shape as described above. A problem here is that accurate evaluation of the pattern dimension is difficult since outer lines of a pattern are not straight lines of a predetermined length in parallel with each other.
One object of the present invention is to provide a mask supply system to shorten the period for manufacturing photomasks.
Another objet of the present invention is to provide a mask supply system to reduce the manufacturing cost of photomasks.
In summary, the present invention is a photomask supply system supplying a photomask to an order-sender. The photomask supply system includes a communication unit, a storage unit, a measuring unit, and a control unit.
The communication unit communicates with the order-sender. The storage unit stores data. The measuring unit measures, according to a measurement recipe, the dimension of a pattern on the photomask which has been produced. The control unit is connected to the communication unit and the storage unit for controlling the communication unit and the storage unit.
The control unit includes a unit for receiving specification data via the communication unit and storing the specification data in the storage unit, the specification data including a dimension-measurement method and mask design data for the pattern formed on the photomask, a recipe generating unit for generating the measurement recipe according to the dimension-measurement method and the mask design data, a calculating unit for calculating to derive, based on the measurement data and the mask design data, production error data for the pattern, and a unit for transmitting the production error data to the order-sender via the communication unit.
Preferably, the control unit further includes a time calculating unit for calculating a measurement time required for measurement performed by the measuring unit based on the specification data, an estimate calculating unit for calculating cost estimate data based on the measurement time, and a transmitting unit for transmitting the cost estimate data to the order-sender via the communication unit.
One advantage of the present invention is thus in reduction of the period for manufacturing photomasks since the production error of the photomask is derived by calculation.
Another advantage of the present invention is in reduction of the manufacturing cost since the time for measurement derived through calculation is used in providing estimate data to the order-sender.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.